Synthetic peptides of the conjugate of ubiquitine and H2A histone

ABSTRACT

Peptides are disclosed possessing some of the immunological properties of the peptide of the formula Gly-Gly-Arg-Leu or Lys-Lys-Thr-Glu, as well as application thereof for screening for certain autoimmune diseases.

BACKGROUND OF THE INVENTION

The object of the present invention is peptides that can be recognizedby antibodies in biological fluids, in particular serums in patients oranimals stricken with auto-immune diseases such as systemic LupusErythematosus or diseases of the nervous systems such as Alzheimer's orParkinson's diseases.

The invention also concerns applications of these peptides andcompositions containing them in in vitro diagnoses in man of thepotentiality of certain auto-immune or nervous-system diseases, as wellas their use in diagnostic kits.

The invention further concerns the application of these peptides in theproduction of immunogenic compositions and of vaccines used againstthese diseases.

Finally, the invention concerns antibodies that can be induced in vivoby these immunogenic peptides and compositions which contain them usedfor in vitro diagnosis in patients stricken with auto-immune ornervous-system diseases, as well as the manufacture of medications usedagainst these diseases.

Stress proteins are involved in a variety of diseases, such as non-viralinfections and certain auto-immune diseases. Thus, S. Muller et al.(Proc. Natl. Acad. Sci., USA 85:8176, 1988) have described ubiquitine, athermal-shock protein containing 76 amino acid residues which is presentin all eukaryote cells as a principal antigenic target of Systemic LupusErythematosus. V. Manetto et al. have shown (Proc. Natl. Acad. Sci., USA85:4501, 1988), that ubiquitine is implicated in diseases of the nervoussystem, such as Alzheimer's and Parkinson's diseases. B. S. Polla(Immunol. Today, 9:134, 1988) has demonstrated that thermal shockproteins may play a central role in all cases of inflammation in which arise in temperature is a significant clinical sign.

It is accepted today that ubiquitine may be present in cells both in thefree state and united with a large number of proteins of the nucleus,the cytoplasm, or the membrane, or may also be linked to the network ofmicrotubules.

The conjugates of ubiquitine of the cytosol are known to be selectivemediators of the breakdown of damaged or abnormal proteins.

In the nucleus, the role of the conjugates of ubiquitine with the H2Aand H2B histones remains poorly understood. The formation of theseconjugates is a product of a selective, reversible histone modification,which occurs most notably in the actively transcribed areas of thechromatin and which may be involved in the relaxation of the chromatin.Ubiquitine may also indirectly modulate the structure of the chromatin,by stimulating the activity of the deacetylase histone enzyme. Anarticle by M. Rechsteiner (Ann. Rev. Cell. Biol., 3:1, 1987) states thatconjugates of ubiquitine with the histones of the nucleus break downmore slowly than those of ubiquitine of the cytosol.

H. Busch et al. (Molec. Cell. biol., 3:1, 1981) and A. W. Thorne et al.(EMBO J., 6:1005, 1987) have described the fact that, in the nucleus,ubiquitine is enzymatically conjugated with histones by means of apeptide bond between the group α-COOH of the C-terminal glycine inposition 76 of the ubiquitine and the group--NH2 of the lateral lysinechain in position 119 in the H2A histone and in position 120 in the H2Bhistone, thus forming branched molecules.

In mammal cells, the H2A and H2B histones conjugated with ubiquitine arepresent in the proportions of 10% and 1%, respectively.

S. Muller et al. have described (Proc. Natl. Acad. Sci., USA 85:8176,1988) the presence, in serums of patients stricken with Systemic LupusErythematosus, of antibodies capable of reacting in an immuno-enzymaticELISA-type test with ubiquitine and with a synthetic fragmentcorresponding to the residues of amino acids 22 to 45 of saidubiquitine.

SUMMARY OF THE INVENTION

More extensive studies have enabled the Applicant to conclude that, inimmuno-transferblot techniques, the serums of patients suffering fromSystemic Lupus Erythematosus also react with two polypeptides havingatomic mass numbers of approximately 52 and 43 kilodaltons andidentified, surprisingly, as contaminants in a commercial ubiquitinepreparation.

By using an antiserum specific for the H2A and H2B histones, theApplicant has shown that these two polypeptides having an atomic massnumber of 43 and 2 kilodaltons corresponded, respectively, to theubiquitine conjugated with the H2A histone and to a mixture ofubiquitine conjugated with the H2A and the H2B histone.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The work carried out on the peptide sequence of the ubiquitine and ofthe conjugates of ubiquitine with the histones has led inventors toprepare synthetic peptides corresponding to the branched part of theconjugate of ubiquitine with the H2A histone. This work has enabled themto confirm the presence of the conjugate of the ubiquitine with the H2Ahistone in polypeptides having atomic mass numbers of 43 and 53kilodaltons.

Antiserums of animals immunized with these peptides react specificallywith the conjugate of the ubiquitine and of the H2A histone, and notwith the H2A histone and/or with the free ubiquitine. Furthermore, theserums of patients stricken with Systemic Lupus Erythematosus reactingimmunologically with the ubiquitine also react with these peptides.

These peptides are thus applicable to the diagnosis of Systemic LupusErythematosus and more broadly, to all autoimmune or nervous systemdiseases in which the conjugate of ubiquitine with the H2A histone playsa role.

The research conducted on these peptides has demonstrated theirimmunogenic importance or capability of being made immunogenic, in orderto induce in vivo the production of antibodies which can recognize theconjugate of ubiquitine with the H2A histone. This conjugate appears toplay an important role in the appearance of auto-antibodies in SystemicLupus Erythematosus, thus indicating strongly the use of these peptidesfor the preparation of a vaccine against this type of disease.

To designate below the amino acid residues which are constituents of thepeptides according to the invention, the following description makes useof a three-letter nomenclature for each natural amino acid, as follows:

    ______________________________________                                               Ala         alanine                                                           Cys         cysteine                                                          Asp         aspartic acid                                                     Glu         glutamic acid                                                     Phe         phenylalanine                                                     Gly         glycine                                                           His         histidine                                                         Ile         isoleucine                                                        Lys         lysine                                                            Leu         leucine                                                           Met         methionine                                                        Pro         proline                                                           Ser         serine                                                            Thr         threonine                                                         Val         valine                                                            Trp         tryptophane                                                       Tyr         tyrosine.                                                  ______________________________________                                    

The peptides according to the invention have immunological properties incommon with the peptide corresponding to the following formula: ##STR1##

The peptides preferred according to the invention have the followingformula: ##STR2## in which:

X and Y represent either an NH2 group which is free or in which amide isintroduced by one or two alkyl groups comprising from 1 to 5 carbonatoms, or a peptide group containing from 1 to 10 amino acid residues,in which the N-terminal amino acid has a free or amide-containing NH2group, as before.

Z represents either a free or alkoxyl OH group which then contains analkyl group comprising 1-5 carbon atoms, or a peptide group containing1-10 amino acid residues, in which the C-terminal amino acid had a freeor alkoxyl OH group, as before.

The groups comprising 1-10 amino acid residues contained in X and/or Yand/or Z are selected essentially so as to preserve the immunologicalproperties of the peptide corresponding to formula (I).

In formula (I), the sequence Gly-Gly-Arg-Leu corresponds to the fractionof the ubiquitine sequence, and the Lys-Lys-Thr-Glu sequence correspondsto the fraction of the H2A histone sequence at the branching pointbetween these two compounds in the conjugate of the ubiquitine with theH2A histone. Thus, the groups containing 1-10 amino acid residuescontained in X and/or Y and/or Z may, in particular, correspond to theadjoining amino acids of the peptide corresponding to formula (I) in theubiquitine-H2A histone conjugate.

Among the formula (II) peptides, preference is given to those in which:

Y represents either a free NH2 group or a Tyr residue containing a freeNH₂ group; X represents a Cys residue whose amine function can possiblybe acetylated; and Z represents an OH group.

Among the formula (II) peptides, preference is given to those in which:

Y represents either a free NH2 group or a Tyr residue containing a freeNH₂ group; X represents the linking of the two Leu and Pro residues, thePro residue being linked by a peptide bond to the adjacent Lys residueof X in formula (II) and the amine function of the Leu residue beingpossible acetylated; and Z represents an OH group.

The invention specifically focuses on peptides corresponding to thefollowing formulae: ##STR3## in which the amine function of the Leuresidue is acetylated (AC); and ##STR4## in which the amine function ofthe Cys residue is acetylated (Ac).

In addition to the above-mentioned peptides, the invention concernspeptides which are modified by the insertion and/or deletion and/orsubstitution of one or several amino acids, as long as the antigenic orimmunogenic properties of said peptides are not modified, as well asthose in which the peptide bond (--C--NH--) is replaced, for example, bythe following structures: --CO--N(CH₃)--, --CH₂ --CH₂ --, --CO--CH₂ --,or again, in which the peptide skeleton has one or several insertedgroups such as the groups --CH₂ --, --NH--, or --O--. The presentinvention also encompasses peptides in which the amino acid residueshaving an asymmetrical carbon are in the form of D or L.

The peptides according to the invention may be prepared usingconventional techniques involving peptide synthesis in the solid phase,either by the successive condensation of the amino acid residues in therequired order, or by condensation of the amino acid residues on apreviously-formed fragment which contains several amino acids in thesuitable order, or, yet again, by condensation of severalpreviously-prepared fragments, taking care to preliminary protect all ofthe reactive functions borne by the amino acid residues or fragments,except for the amine and carboxyl functions involved in the peptide bondformed during condensation.

According to one example of the preparation of a peptide according tothe invention, the Glu residue, whose amine function is protected by aterbutyloxycarbonyl group, is fixed on a resin by means of itscarboxylic group. Next, after removing the protection of the aminefunction by washing the resin with trifluoroacetic acid indichloromethane, the second amino acid residue, whose amine function isprotected as specified above, is linked in dimethylformamide. Thus, theamino acid residues are fixed one after the other, these residuesforming the portion of the peptide according to the invention whichcorresponds to the fraction of the H2A histone sequence. After theremoval of the protection, the amine function of the N-terminal residuecan be acetylated under the effect of an excess of acetic anhydride inthe presence of diisopropylethylamine.

The lateral chains of the trifunctional amino acids must be protected,for example by using the following groups: cyclohexyl for glutamic acid,benzyl for threonine, tosyl for arginine, paramethylbenzyl for cysteine,2,6-dichlorobenzyl for tyrosine, fluorenylmethyloxycarbonyl for one ofthe lysines and 2-chlorobenzyloxycarbonyl for the other lysine.

The lateral chain of the lysine on which branching occurs isadvantageously protected by a fluorenymethoxycarbonyl group. Afterremoval of protection of the lysine using a mixture of piperidine anddimethylformamide, the first glycine residue corresponding to thefraction of the ubiquitine sequence is linked as before. Using thisresidue as a base, the amino acids which will form the peptide chain aregradually linked on the amine group whose protection is preliminarilyremoved on each occasion, the portion already formed remaining attachedto the resin.

After having removed all protective groups, the peptide according to theinvention is removed from the solid substrate, for example usinghydrofluoric acid. The raw product is lyophilized and undergoeschromatography in the liquid phase under medium pressure, thus making itpossible to obtain a product whose purity reaches approximately 93%.This latter is then characterized by using chromatography in the liquidphase under high pressure and by analyzing its amino acid compositionand by mass spectrometry.

Analysis of the amino acid composition of the peptides corresponding toformulae (III) and (IV) gives the following results (expected values aregiven in parentheses):

peptide corresponding to formula (III):

Glx 1.00 (2); Gly 2.00 (2); Arg 0.95 (1); Thr 1.15 (1); Pro 0.95 (1);Tyr 1.02 (1); Leu 1.82 (2); Lys 2.11 (2)

peptide corresponding to formula (IV):

Glx 1.01 (1); Gly 1.97 (2); Arg 0.97 (1); Thr 1.08 (1); Tyr 1.03 (1) ;Cys 0.87 (1); Leu 1.06 (1); Lys 1.87 (2).

The molar mass of the peptides corresponding to formulae (II) and (III),as confirmed by mass spectrometry using the FAB method, are thefollowing (the computed values appear in parentheses):

peptide (III): 1303.8 (1303.5)

peptide (IV): 1196.6 (1196.6).

The stability of the peptides corresponding to formulae (III) and (IV)was verified using HPLC analysis. No deterioration was found afterseveral months of storage at ambient temperature and in the dark,dimerization of the peptide corresponding to formula (IV) is less than9%, because of its terminal Cys residue.

The invention also concerns the conjugates obtained by linking peptidesaccording to the invention to carrier molecules which may bephysiologically acceptable and non-toxic.

Thus, the peptides corresponding to formula (II), in which Y representsa Tyr residue, may advantageously be linked to a carrier protein usingbis-diazobenzidine. According to another embodiment of the invention,the peptides corresponding to formula (II) in which X represents a Cysresidue may be linked to a carrier molecule or to a substrate by meansof a thiol group.

As carrier molecules, natural proteins such as tetanic formol toxoid,albumin, or serum albumins may be mentioned.

The peptides according to the invention possess antigenic properties andmay thus be used in diagnostic procedures for determining, or in thefollow-up of patients stricken with, autoimmune or nervous systemdiseases in which the ubiquitine-H2A histone conjugate is involved. Theinvention further concerns a composition containing at least one of thepeptides liable to be recognized by the antibodies in the serum or anyother biological fluid of patients suffering from these diseases. The invitro detection of the peptide-antibody complex is performed by means ofimmuno-enzymatic ELISA-type, immunofluorescence, radio-immunological, orradio-immunoprecipitation tests.

To perform these tests, the invention also concerns the peptidesaccording to the invention marked using a suitable marker, for examplebiotin or its derivatives, an enzyme like peroxidase, a fluorescentmarker like fluorescein, a radioactive marker such as a radioisotope,etc.

These tests include, for example, the following steps:

deposit of a predetermined quantity of a composition containing apeptide or a conjugate of a peptide according to the invention, in thewells of a titration microplate or on another substrate such as balls;

deposit of the biological fluid to be tested in the wells or incubationof the fluid with the balls;

after incubation or washing of the microplates or balls, deposit in thewells or incubation with the balls of a system for the detection of thepeptide-antibody complex possibly formed.

The immuno-enzymatic ELISA-type tests performed on serums of patientsstricken with systemic Lupus Erythematosus have demonstrated that 96% ofa given population of serums which recognize ubiquitine react with thepeptides corresponding to formula (IV); conversely, only 13% of serumsnot reacting with ubiquitine possess antibodies capable of binding theformula (IV) peptide. Out of the group of patients stricken withsystemic Lupus Erythematosus, 51.8% of serums contain antibodies againstthe H2A histone, and 53.8% of the remainder of these react with theformula (IV) peptide, as against 46.1% which do not react.

The invention further concerns antibodies formed against peptidesaccording to the invention. These antibodies may be polyconal ormonoclonal, and are thus produced by any hybridoma prepared according toconventional methods for producing cellular fusion between the spleniccells of an animal immunized against any of the invention peptides andcells from a line of myeloma cells.

Rabbit antiserums have been prepared based on the formula (IV) peptidelinked to ovalbumin. The antibodies obtained react with neitherubiquitine not the H2A histone during immunoenzymatic ELISA-type tests.Using immunotransfer techniques, these antibodies have made it possibleto show that contaminating fractions having atomic mass numbers of 43and 52 kilodaltons corresponded to ubiquitine-H2A histone conjugates.

Because of the very special branched structure of the inventionpeptides, the antibodies prepared using these peptides constitute veryspecific probes of the ubiquitine-H2A histone conjugates which areincapable of binding free ubiquitine or H2A histone.

While it proved impossible until now to distinguish free ubiquitine fromubiquitine conjugated with the H2A histone, the antibodies according tothe invention make it possible to identify the conjugate unequivocally.

Furthermore, the antibodies formed against the invention peptides andthe auto-antibodies of patients which react with said peptides andobtained after affinity chromatography can be used to prepareanti-idiotype antibodies partially forming an exact copy of the initialantigenic peptide, and which are, therefore, capable of bonding with theauto-antibodies observed in auto-immune diseases.

The present invention also concerns these anti-idiotype antibodies andcompositions containing them, as well as their application in the invitro diagnosis in man of the presence of auto-antibodies and theproduction of medications used to combat these auto-immune diseases.

The invention also concerns immunogenic compositions used to producedvaccines whose active agent is formed by at least one peptide or oneanti-idiotype antibody according to the invention which, possibly linkedto a carrier molecule, leads to the production of antibodies againstsaid peptides and which are capable of interfering with the pathologyand/or clinical manifestations of the auto-immune diseases. Thepharmaceutical compositions according to the invention, which may beused as vaccines, are made up of solutions or suspension which can beinjected or administered by other means and can be administered in dosesof between 10 μg/kg and 100 mg/kg of peptides according to theinvention.

We claim:
 1. An in vitro process for the detection of the presence ofautoantibodies in a biological fluid, said process comprising the stepsof:(a) placing said biological fluid in contact with at least onepeptide having the formula ##STR5## wherein X is NH_(Z), Cys, orLeu-Pro, wherein NH_(Z) moieties are optionally substituted withhydrogen, C₁₋₅ alkyl, or acetyl, Y is NH₂ or Tyr, wherein NH₂ moietiesare optionally substituted with C₁₋₅ alkyl or acetyl, and Z is OH, orC₁₋₅ alkoxy, or placing said biological fluid in contact with aconjugate of said peptide and a carrier molecule; (b) forming apeptide-autoantibody complex or a conjugate-autoantibody complex; and(c) detecting the presence or absence of said peptide-autoantibodycomplex or said conjugate-autoantibody complex in said biological fluid.2. An in vitro process for the detection of autoantibodies associatedwith systemic lupus erythematosis in a biological fluid, said processcomprising the steps of:(a) contacting said biological fluid with apeptide having the formula ##STR6## wherein X is NH₂, Cys, or Leu-Pro,wherein NH₂ moieties are optionally substituted with hydrogen, C₁₋₅alkyl, or acetyl, Y is NH₂ or Tyr, wherein NH₂ moieties are optionallysubstituted with C₁₋₅ alkyl or acetyl, and Z is OH, or C₁₋₅ alkoxy, orplacing said biological fluid in contact with a conjugate of saidpeptide and a carrier molecule, under conditions suitable for formingimmunological complexes; and (b) detecting the presence or absence ofimmunological complexes containing the autoantibodies.
 3. An in vitroprocess for the detection of autoantibodies associated with systemiclupus erythematosis in a biological fluid, said process comprising thesteps of:(a) contacting said biological fluid with a peptide having theformula ##STR7## or placing said biological fluid in contact with aconjugate of said peptide and a carrier molecule, under conditionssuitable for forming immunological complexes; and (b) detecting thepresence or absence of immunological complexes containing theautoantibodies.
 4. An in vitro process for the detection ofautoantibodies associated with systemic lupus erythematosis in abiological fluid, said process comprising the steps of:(a) contactingsaid biological fluid with a peptide having the formula ##STR8## orplacing said biological fluid in contact with a conjugate of saidpeptide and a carrier molecule, under conditions suitable for formingimmunological complexes; and (b) detecting the presence or absence ofimmunological complexes containing the autoantibodies.